A variety of electrochemical applications are based on electrochemical cells which contain a reference electrode as one of the electrodes in the cell. The term "reference electrode" is used to refer to an electrode which provides a stable, constant potential regardless of the type, or concentration, of species present in the fluid in which the reference electrode is placed. Thus, one can detect meaningful changes in the potential of an indicator electrode which is paired with a reference electrode. These meaningful changes can be detected by comparing the changes in the paired indicator electrode to the constant potential of the reference electrode. These comparative changes can be used in detecting the presence of a wide variety of species in a solution, where the species influences the potential at the indicator electrode.
Many different reference electrode structures have been designed for use under a variety of conditions, e.g. temperature, pressure and chemical conditions. Exemplary reference electrodes include the hydrogen electrode, the calomel electrode and the silver/silver chloride electrode. Although each of these reference electrodes provides a constant potential in the environments for which they are designed, these electrodes have limitations as to the temperature, pressure and chemical conditions in which they may be employed. For example, hydrogen electrodes cannot be used in oxidizing or reducing environments, or in solutions which poison the metal of the electrode. Saturated calomel electrodes can be used with a wider array of solutions, but are limited to operation at room temperature because of chemical, mechanical and safety concerns.
Thus, there is continuing interest in the development of new reference electrode structures which are stable under a wide range of conditions. Such electrodes would not be limited to a particular use, thus allowing for greater flexibility in application.